Electron tube



Patented July 21, 1953 ELECTRON TUBE David A. Sokolov, Lynn, Mass-., assignor to Hytron Radio & Electronics 00., Salem, 'Mass., at division of Columbia Broadcasting System, Inc., a

corporationofNew York Application July 5, 1952, Serial No. 297,217

This invention relates in general to electron tubes and in particular to stems for such tubes.

It is the usual practice to bring leads into a vacuum tube either by means of a stem press or a button press. The leads in such structures are separated by the glass through which they are sealed. Because these structures provide insufiicient insulation and short leakage paths between separate leads, high voltage leads are usually introduced through the top or side of the tube envelope where they are isolated from other leads which pass through the stem.

In tubes designed for high altitude operation, leads which are at relatively low potentials require similar protection, because insulation and leakage problems are present even at these low potentials due to the lower atmospheric pressure encountered. However, it has proven undesirable to treat these leads as high voltage leads and bring them through the top or sides of the tube envelope for several reasons. The circuitry about the tube becomes more involved with the need for longer leads and the additional space requirements for accommodating such leads with connectors for top and side caps. Also, the assembly of the tubes is more difficult, additional operations being required.

Continuing to run the leads through the stem and base and adding an insulating material within the base is objectionable forsimilar reasons,

more operations and more material being required. Too, the results of such an expedient are somewhat unreliable in so far as a-solution to the problem is concerned.

Another factor complicating the problem of high altitude operation of electron tubes derives from the fact that tubes in those applications are often exposed to severe shock hazards. To aid .these tubes in withstanding shock, the elements are usually supported by dummy leads as well as by conducting leads which pass through the stem to base pins. To prevent arcing involving the dummy leads outside the tube envelope, the obvious expedient is to bury them in the glass of the press so that they arenot exposed externally. In

the so-called flat stem press, dummy leads are invariably so buried. The flat stem press is made usually by having a head over which a flareFis dropped. The head has several openings lying in a plane and facing upwardly. The leads which are three-part structures have a flexible portion for threading into the base pins, a short Dumet section for sealing to the flare, and a stifi portion on which tubeelements are to be mounted, The

stiff portions are placed in the holes of the-head,

" .7. Claims. (Cl...3l3245) a tubulating member is jigged from above, and the Whole assembl is then rotated in flames of various necessary heating capacities and the stem is finally formed by two flat hammer members closing on the now soft glass to seal it to the leads. Air is blown through the tubulation and a communicating entry thus formed. If dummy leads were needed for additional electrode sup port, they were formed by merely inserting twopart leads having no flexible portion. Theseleads in the completed stem were sufliciently short that no portion could extend above the sealed glass of the stem, to be externally exposed in a finished tube.

In the manufacture of button stems having integral tubulations, however, a different technique has been widely adopted. The nature of the stem demands that the molds work in a vertical plane rather than the horizontal plane as in the flat stem press. Hence, the machine heads are made with a circular array of small openings into which the flexible portions of the leads are dropped. A larger central opening accommodates the tubulation. A cylinder of glass is placed about the leads and the cylinder is flattened by various molds into a button in the successive machine positions, the glass being finally sealed by flames working against a centrally pointed mold to the tubulation. Because only the stiiT portions of the leads extend upwardly, the downwardly moving mold member can easily be provided with openings: to

eachposition. Obviously, deterioration of such a clamp wou'ld'be rapid and objectionable.

It has long been recognized that a technique adaptable to existing machinery but retaining the benefit 'of dummy leads for support and without substantial loss of high voltage characteristics associated with buried dummy leads would be a worthwhile advance in the art of stem making.

Therefore'it is an object of the present invention to'provide a tube capable of operation at high altitudes.

It is another object to provide high altitude tubes which do not require more materials and operations than conventional tubes.

It is a further object to provide a stem for a high altitude tube which may be fabricated without departure from high-speed stem making techniques.

It is a still further object of this invention to provide a high altitude tube which requires no special circuitry or connections.

In general, the present invention consists of an electron tube having stem and mount connections which utilize available sealing glass efiiciently to minimize the possibility of high voltage arcs causing short circuits between leads entering the tube. By the same construction leakage paths are increased to a maximum length for the size of the stem. The objectives are accomplished by the inclusion of concave depressions on the external side of the button press surrounding each of the leads. Those leads between which arcing might otherwise be likely to occur are terminated at the deepest points of their concave depressions. For a better understanding of the invention, together with other and further objects, features, and advantages, reference should be made to the following description which is to be read in connection with the accompanying drawing, the single figure of which is an elevation view, partly cut away to show details of the button stem and mount.

Referring particularly to the drawing, there is shown a rectifier tube having an envelope l4 containing a first anode l6 and a second anode IS. A first filament l3 and a second filament l cooperate with anodes l5 and i8 respectively to provide a double rectifier. The rectifier illustrated is one in which a mount of the shock-proof type is used. Anode I3 is supported by the leads and 22. Lead 23 passes through the button being sealed thereto at a central point in cavity 24 and being connected to base pin 2|. Lead 22 also passes through the button but is a dummy lead terminated at a central point in cavity 28 fiush with the glass forming the bottom of the cavity. A tubulation IT is sealed centrally of the button to permit exhausting of the tube. Tubulation ll terminates in a tip (not shown) within the tube key.

Anode I8 is similarly supported by two leads,

one lead passing through its cavity and being connected to a base pin 2?, and a dummy lead terminating at the bottom point of its cavity. Filament [3 is connected in series with filament [5 by means of a conductor 28 which is two-point supported by dummy leads, (not shown), which i are sealed through the button but which also terminate at the bottom surfaces of their respective cavities. One end of filament I3 is connected to a lead 30 and one end of filament I5 is connected to a lead 32. Leads 30 and 32 pass through their respective cavities and are connected to base pins 33 and 35 respectively, whence operating filament voltage is derived.

The button itself as viewed from outside the tube is illustrative of the efficiency of use of available glass for mechanical ruggedness of structure and for insulating advantages. All eight of the external cavities and their corresponding internal protrusions are utilized to provide maximum support to the mount, but in such a fashion that the greatest possible separation of leads between which arcing might be encountered is made. Lead 29, connected from anode [6 to base pin 2| may be taken as a starting point, and, going in a clockwise direction, the next adjacent cavity contains only the blanked end of lead 22 which provides additional support to anode 15. Next, lead 30 appears, supporting filament l3 and connected to base pin 33. The next lead encountered is lead 2 which is connected from filament 15 to base pin 35, followed by a dummy lead, (not shown). which is terminated at the base of its cavity and gives support to anode [8 within the tube, followed by an active lead connecting anode 18 to a base pin. The next two leads are dummy leads which support conductor 23, the filament midpoint.

Th structure of the button stem of the invention is such that the points between which arcing would be most likely to occur are widely separated and offer small areas, as at the ends of the dummy leads, which are hidden from the electric fields about other leads external to the base. The points having greatest voltage differences in the embodiment shown would normally be any given filament lead and any given plate lead. As noted hereinabove, separation of the high and low voltage points is maximized by the choice of positions about the circular button through which the leads pass. Wherever it is necessary for a filament lead to be located near a plate lead, or vice versa, one of the leads is snapped off at its cavity base to remove it from the effect of fields surrounding the lead of differing voltage. The use of glass beads about the leads, protruding outwardly would not accomplish a similar function of hiding the exposed ends from the fields of other leads, although leakage paths would be of similar length.

Further, and more important, conventional button fabrication techniques are utilized, since the leads are originally of full length extending down into the heads of the stem machine. No special jigs are needed, and the desired leads are merely snapped OK at the bases of their cavities, and the stem is ready for further processing.

While what has been disclosed is a preferred embodiment, it is believed that the concept of providing external recesses or cavities surrounding the tube leads and the concept of blanking off desired leads are within the scope of the invention. Modification of the button to provide external recesses of difierent configuration may be desirable in some instances but is also believed to be within the scope of the invention which should be limited only by the breadth of the appended claims.

What is claimed is:

1. An electron tube comprising, an evacuated envelope, a button stem forming a portion of said envelope, said button stem comprising, a glass disk, a plurality of leads sealed through said disk, said leads being symmetrically arrayed in a circle adjacent the periphery of said disk, a cavity being formed in the external side of said disk about each of said leads, a first group of said leads extending completely through said disk and beyond it on either side, the remainder of said leads being terminated on the external side of said disk at points within their respective cavities substantially flush with the cavity walls.

2. An electron tube comprising, an evacuated envelope, at least a filament and an anode within said envelope, a glass button forming the base of said envelope, a plurality of leads sealed through said button, a base attached to said envelope and substantially enclosing said button, conductive base pins extending outwardly from said base, at least a first lead connected from said filament to one of said base pins, a second lead connected from said anode to a second of said base pins, and a third lead connected to and supporting said filament terminating flush with the bottom surface of the cavity formed thereabout said leads being sealed through said button, an outwardly facing cavity being formed in said button surrounding each of said leads.

3. Apparatus as in claim 2 including an auxiliary lead also connected to said anode and sealed through said button, an outwardly facing cavity being formed in said button about said auxiliary lead, said auxiliary lead being terminated substantially at the innermost surface of the cavity formed thereabout.

4. An electron tube comprising, an evacuated glass envelope, at least a filament and an anode within said envelope, a glass button forming the base of said envelope, a first plurality of leads connected to said filament and sealed through said button, a second plurality of leads sealed through said button and connected to said anode, an outwardly facing cavity being formed in said button surrounding each of said leads, at least one of said plurality of leads extending outwardly beyond said button, each of th remainder of said first plurality of leads being terminated substantially at the innermost surface of the cavity formed thereabout, at least one of said second plurality of leads extending outwardly beyond said button, each of the remainder of said second plurality of leads being terminated substantially at the innermost surface of the cavity formed thereabout.

5. An electron tube for high altitude use comprising, an evacuated envelope, a glass button forming the base of said envelope, a pair of anodes and cooperating filaments within said envelope forming a double rectifier, a group of eight recesses formed in the external side of said button, said recesses being arrayed in a circle adjacent the periphery of said button, a base cemented to said envelope and including five base pins, said base pins being arranged in a group of three adjacent pins, and two base pins, separated from each other and from said group of three by a distance-twice as great as that separating each pin of said group of three, eight leads being sealed into said button, each being centrally disposed within one of said recesses, one of said leads being connected from each of said anodes to one of said two base pins, one of said leads being connected from one end of each of said filaments t0 the end ones of said group of three adjacent base pins, the remainder of said leads each being terminated at the deepest point of its recess, one lead of said remainder supporting each of said anodes, two adjacent leads of said remainder supporting the junction of said filaments.

6. An electron tube comprising, an evacuated envelope, a button stem forming a portion of said envelope, said button stem comprising, a plurality of leads sealed through a glass disk, a cavity being formed in said disk on the external side of said tube about each of said leads, a first group of said plurality of leads extending beyond the outer surface of said disk, and the remainder of said plurality of leads being terminated substantially at the bottom surface of their respective cavities.

'7. An electron tube comprising, an evacuated glass envelope having a button forming one end thereof, said button stem including a plurality of leads sealed through a glass disk, an external cavity being formed in said glass disk about each of said leads, a first group of said plurality of leads extending beyond the external surface of said disk, the remainder of said leads being terminated substantially at the bottom surface of their respective cavities, a tube base attached to said envelope and having a plurality Of connecting pins arrayed thereabout, said first group of leads being arranged in said stem and connected to those of said pins in a manner providing optimum spacing between each of said first group of leads and each of those of said remainder.

DAVID A. SOKOLOV.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date D. 128,301 Miller July 15, 1941 D. 132,858 Miller June 23, 1942 1,941,687 Hunter, Jr Jan. 2, 1934 2,174,375 Beggs Sept. 26, 19 9 2,219,758 Baier et a1 Oct. 29, 1940 

